- Allium sativum
- 2-propenesulfenic acid, AGE, aged garlic extract, aglio (Italian), aglio commune (Italian), ail (French), ail blanc (French), ail commun (French), ail cultivé (French), ail de printemps (French), ail rose sans bâton (French), ajo (Spanish), ajo común (Spanish), ajo vulgar (Spanish), ajoene, akashneem, alho (Portuguese – Portugal, Portuguese – Brazil), ), alho-bravo (Portuguese – Brazil), alho-comum (Portuguese – Brazil), alho-hortense (Portuguese – Brazil), alisat, alk(en)yl thiosulfates, Alliaceae (family), allicin, Allicor® (a long-action, garlic-based preparation), Allii sativi bulbus, alliinase, allitridium, allium, allyl mercaptan, Alterswurzel (German), alubosa elewe, Amaryllidaceae (family), ayo-ishi, ayu, banlasun, bawang (Tagalog), bawang bodas (Sundanese), bawang puteh (Malay), bawang putih (Malay – Indonesia, Malay – Java), beli luk (Serbian), bellulli (Kannada), bhabang poté (Madurese), ca suan (Chinese), ca suan tou (Chinese), camphor of the poor, česen (Slovenian), cesnak kuchynský (Slovenian), česnek kuchyňský (Czech), česnek kuchyňský pravý (Czech), češnjak (Croatian), chesnok (Russian), chyet thon phew (Burmese), clove garlic, czosnek (Polish), czosnek pospolity (Polish), dai toan, da-suan, dasuan, dawang, diallyl disulphide (DADS), diallyl sulfide (DAS), diallyl sulphide, diethyl disulfide, diethyl hexasulfide, diethyl monosulfide, diethyl pentasulfide, diethyl tetrasulfide, diethyl trisulfide, dipropyl disulphide, dipropyl sulphide, dra thiam, (E)-ajoene, echter Knoblauch (German), fokhagyma (Hungarian), foom, gaarikku (Japanese), garlic clove, garlic corns, garlic extract, garlic oil, garlic paste, garlic powder extract, Gartenlauch, gemeiner Knoblauch (German), gewöhnlicher Knoblauch (German), hom khaao, hom kia, hom thiam (Thai), hua thiam, hvid-løg (Danish), hvidløg (Danish), hvitløk (Norwegian), hvitlök (Swedish), kath’ièm (Laotian), kesumphin, khtüm sââ (Khmer), kitunguu-sumu (Swahili), kitunguu-sumu, Knoblauch (German), Knöblich (German), Knofel (German), knoflook (Dutch), Knuflauk (German), Knuflook (German), konofló (Papiamento – Curaçao), kra thiam, krathiam (Thai), krathiam cheen, krathiam khaao, küüslauk (Estonian), Kwai®, Kyolic®, lahasun (Hindi), lahsan (Hindi), lahsun, lai, l’ail, la-juan, larsan (Hindi), lasan, lashun, lashuna (Kannada), lashunaa (Sanskrit), la-suan, lasun (Hindi, Nepalese, Punjabi), lasuna, lasuun (Marathi), lauch, lay, layi, lehsun (Urdu), lesun, Liliaceae (family), lobha, luk chesnok (Russian), luk posevnoi (Russian), ma nul (Korean), majo, methyl allyl, naharu, nectar of the gods, ninniku (Japanese), pa-se-waa, poor man’s treacle, purgar garlic, PurGar garlic, rason, rasonam, rasun (Bengali), rocambole, rust treacle, rustic treacles, S-alk(en)yl cysteine sulfoxide, S-allylcysteine (SAC), sarımsak (Turkish), sarmesak (Turkish), sarmusak (Turkish), saum (Arabic), seer (Persian), sekhdor (Aremenian), shoum (Hebrew), shum (Hebrew), sir (Persian), skorda (Greek), skordo (Greek), skordon (Greek), skortho (Greek), sluon, Stinkerzwiebel (German), stinking rose, suan (Chinese), sudulunu (Sinhalese), tafanuwa, ta-suam, ta-suan, tellagada, tellagaddalu (Telugu), tetrasulfides, thawm (Arabic), thiam, thioallyl derivative, thiosulfinates, thoum thum (Arabic), t?i (Vietnamese), toi thum, toom (Arabic), toum (Arabic), trisulfides, tum, umbi bawang putih, vallaippundu (Finnish), velluli (Telugu), vallaippundu (Malayalam), vellaippuuntu (Tamil), vellaypoondoo (Tamil), vellulli (Telugu), verum, vinyl dithiin, vinyldithiin, vitloek (Swedish), vitlök (Swedish), vitløk (Swedish), wullaypoondoo (Tamil), (Z)-ajoene.
- Combination products: Karinat® (beta-carotene 2.5 milligrams, alpha-tocopherol 5 milligrams, ascorbic acid 30 milligrams, and garlic powder 150 milligrams per tablet).
- Garlic is a culinary herb that is widely used for the treatment and prevention of cardiovascular disease and cancer. Numerous controlled trials have examined the effects of oral garlic on serum lipids. Long-term effects on lipids or cardiovascular morbidity and mortality remain unknown. Other preparations (such as enteric-coated or raw garlic) have not been well studied.
- Small reductions in blood pressure (
- Numerous case-control/population-based studies suggest that regular consumption of garlic (particularly unprocessed garlic) may reduce the risk of developing several types of cancer, including gastric and colorectal malignancies. However, prospective controlled trials are lacking.
- Multiple cases of bleeding have been associated with garlic use, and caution is warranted in patients at risk of bleeding or prior to some surgical/dental procedures. Garlic does not appear to significantly affect blood glucose levels.
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.
Numerous human studies report that garlic may lower blood pressure.
Multiple studies in humans have reported small reductions in total blood cholesterol and low-density lipoproteins (“bad cholesterol”) over short periods of time (4 to 12 weeks). Effects on high-density lipoproteins (“good cholesterol”) are unclear. This remains an area of controversy.
Garlic may prevent future heart attacks. The effects of garlic on cholesterol levels may be beneficial.
Application of garlic gel on the skin may be beneficial in the treatment of alopecia areata (hair loss). Additional study is needed.
Preliminary evidence suggests that garlic reduces episodes of uncontrolled angina by relieving spasm of the coronary vessels and antithrombotic action. Well-designed clinical trials are needed before a conclusion can be made.
Preliminary evidence suggests that garlic has antibacterial effects. Well-designed clinical trials are needed before a conclusion can be made.
Several studies describe the application of garlic to the skin to treat fungal infections, including yeast infections. Take caution as garlic can cause severe burns and rash when applied to the skin of sensitive individuals.
Preliminary research in humans suggests that deposits of cholesterol in blood vessels may not grow as quickly in people who take garlic. It is not clear if this is due to the ability of garlic to lower cholesterol levels or to other effects of garlic.
Based on preliminary study, allicin (the major biologically active component of garlic) supplementation may reduce exercise induce muscle damage. The mechanism may be associated with allicin’s antioxidant effects. Further studies are needed to confirm these findings.
A single administration of garlic resulted in increased endurance performance in humans. Long-term use of garlic for this purpose should be investigated.
Taking garlic supplements by mouth may improve some symptoms of benign breast disease. Additional study is needed.
Preliminary human studies suggest that regular consumption of garlic (particularly unprocessed garlic) may reduce the risk of developing several types of cancer including gastric and colorectal malignancies. Some studies use multi-ingredient products so it is difficult to determine if garlic alone may play a beneficial role. Further well-designed human clinical trials are needed to conclude whether eating garlic or taking garlic supplements may prevent or treat cancer.
Human studies suggest modest short-term reductions in total cholesterol and low-density lipoprotein levels have with garlic supplements. There is limited evidence regarding the effects of garlic on cardiac morbidity and mortality, and it is currently unclear if garlic reduces the incidence of heart attack or cardiac death.
Based on observational study, garlic supplementation increased calf blood flow in healthy individuals. Further research is needed before conclusions can be made.
Familial hypercholesterolemia is a genetic disorder in which very high cholesterol levels run in families. Research in children with an inherited form of high cholesterol suggests that garlic does not have a large effect on lowering cholesterol levels in these patients.
Preliminary evidence suggests that a combination product containing garlic (Karinat®) may be beneficial in the management of chronic atrophic gastritis, a precursor of stomach cancer. Additional evidence is needed before a conclusion can be made.
Early studies in humans show a lack of an effect of garlic on gastric or duodenal ulcers.
There is currently not enough evidence to suggest that garlic helps repel mosquitoes.
Preliminary evidence suggests that a combination product containing garlic (Naturopathic Herbal Extract Ear Drops [NHED]) may be beneficial for ear pain caused by acute otitis media in children. Additional evidence is needed before a conclusion can be made.
Some human studies suggest that garlic may be effective against parasitic infections. Better-designed studies are needed.
Some human studies suggest that garlic may improve circulation in the legs by a small amount, but this issue remains unclear. Better-designed studies are needed.
There is not enough evidence to recommend increased garlic intake for preventing pre-eclampsia and its complications.
Initial evidence suggests the antioxidant activity of garlic may benefit sickle cell anemia. Further study is necessary.
There is insufficient evidence to recommend the use of garlic in systemic sclerosis.
In early study, self-reports of tick bites were significantly less in people receiving garlic over a placebo “sugar” pill. Further well-designed study is needed to confirm these results.
Animal studies suggest that garlic may lower blood sugar and increase the release of insulin, but studies in humans do not confirm this effect.
Preliminary reports suggest that garlic may reduce the severity of upper respiratory tract infections. However, this has not been demonstrated in well-designed human studies.
Based on preliminary research, topical use of garlic aqueous extract or lipid extract may beneficial in the treatment of warts and corns. Further study is needed.
*Key to grades:
The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.
Adults (18 years and older)
- Human studies report the use of 4-12.3 milligrams of garlic oil by mouth daily. Some sources report that steam-distilled oils, oil from crushed garlic, and aged-garlic in alcohol may be less effective for some uses, particularly as a blood thinner.
- 600 to 900 milligrams daily of non-coated, dehydrated garlic powder in three divided doses, standardized to 1.3% allicin content, has been used in human studies. The European Scientific Cooperative on Phytotherapy (ESCOP) recommends 3 to 5 milligrams allicin daily (1 clove or 0.5 to 1.0 gram dried powder) for the prevention of atherosclerosis. The World Health Organization (WHO) recommends 2 to 5 grams fresh garlic, 0.4 to 1.2 grams of dried powder, 2 to 5 milligrams oil, 300 to 1,000 milligrams of extract, or other formulations that are equal to 2 to 5 milligrams of allicin daily.
- The European Scientific Cooperative on Phytotherapy (ESCOP) recommends 2 to 4 grams of dried bulb or 2 to 4 milliliters of tincture (1:5 dilution in 45% ethanol), by mouth three times a day for upper respiratory tract infections.
- Garlic oil preparations (4-12.3 milligrams) have been used in human studies. For athletic performance, 900 milligrams of odor-modified dried garlic has been taken. For cancer prevention, aged garlic extract capsules (containing 2.4 milliliters of garlic extract) daily for 12 months. For heart disease risk prevention, Allicor® (150 milligrams of garlic powder), one tablet two times daily for 12 months. For cholesterol- and blood pressure-lowering effects, 600-1200 milligrams per day of garlic powder in three divided doses, standardized to 1-3% allicin content, has been used. For Helicobacter pylori infection, allicin (a main ingredient in garlic), 4200 micrograms daily in conjunction with standard treatment for 14 days, has been used. For peripheral vascular disease, 800 milligrams of dehydrated garlic daily (Kwai®) for 12 weeks. For sickle cell anemia, 5 milliliters of aged garlic extract for four weeks. For systemic sclerosis, 900 milligrams of dried garlic powder for seven days has been used.
- Garlic paste has been applied to the skin, four times daily, for 14 days to treat oral candidiasis. Garlic extract has been applied twice daily on warts. For alopecia areata, a 5% garlic gel has been applied to the skin four times daily for three months.
- As an antifungal treatment, one milligram per kilogram of body weight per day of garlic extract diluted into 500 milliliters of saline, administered intravenously (through the veins) over four hours for less than one month.
Children (younger than 18 years)
- Safety or effectiveness of garlic supplements has not been proven in children. Garlic in amounts found in food is likely safe in most children.
- One study in children (ages 8-18 years) with possible familial hyperlipidemia used 900mg of garlic powder tablets (Kwai®) in three divided daily doses.
The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.
- People with a known allergy to garlic, any of its ingredients, or to other members of the Liliaceae (lily) family, including hyacinth, tulip, onion, leek, and chives, should avoid garlic. Allergic reactions have been reported with garlic taken by mouth, inhaled, or applied to the skin. Some of these reactions are severe including throat swelling and difficulty breathing (anaphylaxis). It has been suggested that some cases of asthma from inhaling garlic may be due to mites on the garlic. Fresh garlic applied to the skin may be more likely to cause rashes than garlic extract.
Side Effects and Warnings
- Bad breath, body odor, and allergic reactions are the most common reported side effects of garlic. Fresh garlic has caused rash or skin burns, both in people taking garlic therapy and in food preparers handling garlic. Most reactions improve after stopping garlic therapy. Other reported side effects include dizziness, stomach pain, anorexia, diarrhea, nausea, vomiting, gas, weight loss, belching, heartburn, constipation, facial flushing, increased heart rate, insomnia, increased sweating, headache, itching, fever, chills, asthma flares, and runny nose.
- Bleeding is a potentially serious side effect of garlic use, including bleeding after surgery and spontaneous bleeding. Several cases of bleeding are reported, which may be due to effects of garlic on blood platelets, or to increased breakdown of blood clots (fibrinolysis). There is debate about the effects of garlic in people treated with warfarin (Coumadin®), but studies suggest that garlic does not alter the International Normalized Ratio (INR) values that are used to measure the effect of warfarin on blood thinning. Garlic should be stopped prior to some surgical or dental procedures due to an increased risk of bleeding. Caution is urged for people who have bleeding disorders or who take blood thinning medications (anticoagulants, aspirin/anti-platelet agents, non-steroidal anti-inflammatory drugs such as ibuprofen or naproxen) or herbs/supplements that may increase the risk of bleeding. Dosing adjustments may be necessary.
- Garlic or its ingredients may lower blood sugar levels and increase the release of insulin. However, studies in humans do not show changes in blood sugar control in people with or without diabetes. Nonetheless, caution is advised in people with diabetes or hypoglycemia, and in those taking drugs, herbs, or supplements that affect blood sugar. Blood sugar levels may need to be monitored by a healthcare professional, and medication adjustments may be necessary. Informal reports describe low iodine absorption in the thyroid and low levels of thyroid hormone (hypothyroidism) with garlic supplementation. A few reports suggest that garlic and garlic-like plants may be linked to nodules or tumors of the thyroid. Reduced sperm counts have been reported in rats.
- Dehydrated garlic preparations or raw garlic taken by mouth may cause burning of the mouth, abdominal pain or fullness, poor appetite, gas, belching, nausea, vomiting, irritation of the stomach lining, changes in the bacteria in the gut, heartburn, diarrhea, or constipation. One report describes bowel obstruction in a man who ate a whole garlic bulb. Garlic should be used cautiously by people with stomach ulcers or who are prone to stomach irritation.
- Multiple studies show a small reduction in blood cholesterol levels after garlic supplements are taken by mouth. Small reductions in blood pressure are also commonly reported. One case of heart attack is noted in a healthy man after taking a large amount of garlic by mouth.
- Use cautiously in individuals with peptic ulcer disease or in individuals prone to stomach irritation.
- Use cautiously in patients taking antiretroviral drugs, blood pressure lowering medications, drugs that are metabolized by the liver, vasodilators, or fish oil.
- Contamination of garlic products has been reported. In Vancouver, British Columbia, a commercial preparation of chopped garlic was linked to botulism. One report describes overdose of colchicine and even death after meadow saffron (Colchicum autumnale) was mistaken for wild garlic (Allium ursinium).
- Garlic and Pycnogenol® have been shown to increase human growth hormone secretion in laboratory experiments.
Pregnancy and Breastfeeding
- Garlic is likely safe during pregnancy in amounts usually eaten in food, based on historical use. However, garlic supplements or large amounts of garlic should be avoided during pregnancy due to a possible increased risk of bleeding. In addition, early animal studies suggest that garlic may cause contraction of the uterus. Many tinctures contain high levels of alcohol, and should be avoided during pregnancy.
- Garlic is likely safe during breastfeeding in amounts usually eaten in food, based on historical use. However, some mothers who take garlic supplements report increased nursing time, milk odor, and reduced feeding by the infant. The safety of garlic supplements during breastfeeding is not known.
The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.
Interactions with Drugs
- Human reports suggest that garlic may increase the risk of bleeding when taken with drugs that also increase the risk of bleeding. Examples include aspirin, anticoagulants (“blood thinners”) such as warfarin (Coumadin®) or heparin, anti-platelet drugs such as clopidogrel (Plavix®), and non-steroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®). Animal and human studies show that garlic can lower blood pressure. Use cautiously when combining with other medications that lower blood pressure. Several human studies report lower cholesterol in people taking garlic. These effects may be increased if garlic is taken with medications that lower blood cholesterol like lovastatin (Mevacor®) or other “statins” (HMGCoA reductase inhibitors).
- Levels of the drug saquinavir, used in HIV treatment, may be reduced if garlic is taken, and its effectiveness may therefore be reduced. Other antiviral drugs like ritonavir may also be affected.
- Garlic may lower blood sugar levels. Although this is theoretical in humans, caution is advised when using medications that may also lower blood sugar. Patients taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare professional. Medication adjustments may be necessary. Individuals with thyroid disorders or who take thyroid medications should use caution in taking garlic supplements as they may affect the thyroid.
- Garlic may alter levels of certain drugs metabolized by the liver’s CYP450 enzyme system.
- Many tinctures contain high levels of alcohol, and may cause nausea or vomiting when taken with metronidazole (Flagyl®) or disulfiram (Antabuse®).
- Garlic may alter levels of various anti-cancer drugs. Check with your oncologist and pharmacist before starting to take garlic supplements.
- Garlic may increase the effects of acetaminophen, anthelmintics, antibiotics, antifungals, antiglaucoma agents, antiobesity agents, drugs used for osteoporosis, estrogens, neurologic agents, performance-enhancing agents, potassium salts, or vasodilators.
- Garlic may decrease the effectiveness of fertility agents or drugs used to suppress the immune system,
Interactions with Herbs and Dietary Supplements
- Garlic may increase the risk of bleeding. In theory, this risk may be further increased when garlic is taken with other herbs or supplements that also increase the risk of bleeding. Multiple cases of bleeding have been reported with the use of Ginkgo biloba and two cases with saw palmetto. Numerous other agents may theoretically increase the risk of bleeding, although this has not been proven in most cases.
- Vitamin E may have positive effects on cardiovascular disease and atherosclerosis. Taking garlic with vitamin E may increase these effects.
- Garlic may have a small effect in lowering blood pressure. Caution should be used if taken with other supplements that can lower blood pressure.
- Garlic may lower blood sugar levels. Caution is advised when using herbs or supplements that may also lower blood sugar. Blood glucose levels may require monitoring, and doses may need adjustment.
- Garlic may lower cholesterol a small amount. These effects may be larger than expected if taken with other cholesterol-lowering supplements such as fish oil. Individuals with thyroid disorders or who take thyroid medications should use caution in taking garlic supplements as they may affect the thyroid.
- Garlic may interact with herbals and dietary supplements that are metabolized by the liver’s CYP450 enzyme system.
- Garlic and Pycnogenol® have been shown to increase human growth hormone secretion in laboratory experiments.
- Garlic may alter levels of various herbs with anti-cancer properties. Check with your oncologist and pharmacist before starting to take garlic supplements.
- Garlic may increase the effects of anthelmintics, antibacterials, antifungals, intraocular pressure-altering herbs, antiobesity herbs and supplements, antioxidants, herbs and supplements used for osteoporosis, phytoestrogens, fish oil, neurologic herbs and supplements, performance-enhancing herbs and supplements, potassium, selenium, vasodilators, or zinc.
- Garlic may decrease the effectiveness of fertility agents or herbs and supplements used to suppress the immune system.
Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy.
- This information is based on a systematic review of scientific literature edited and peer-reviewed by contributors to the Natural Standard Research Collaboration ().
- Ashraf R, Aamir K, Shaikh AR, et al. Effects of garlic on dyslipidemia in patients with type 2 diabetes mellitus. J Ayub Med Coll Abbottabad 2005 Jul-Sep;17(3):60-4.
- Gail MH, You WC. A factorial trial including garlic supplements assesses effect in reducing precancerous gastric lesions. J Nutr 2006 Mar;136(3 Suppl):813S-815S.
- Hajheydari Z, Jamshidi M, Akbari J, et al. Combination of topical garlic gel and betamethasone valerate cream in the treatment of localized alopecia areata: a double-blind randomized controlled study. Indian J Dermatol Venereol Leprol 2007 Jan-Feb;73(1):29-32.
- Josling P. Preventing the common cold with a garlic supplement: a double-blind, placebo-controlled survey. Adv Ther 2001;18(4):189-193.
- Kim, J. Y. and Kwon, O. Garlic intake and cancer risk: an analysis using the Food and Drug Administration’s evidence-based review system for the scientific evaluation of health claims. Am.J Clin Nutr. 2009;89(1):257-264.
- McNulty CA, Wilson MP, Havinga W, et al. A pilot study to determine the effectiveness of garlic oil capsules in the treatment of dyspeptic patients with Helicobacter pylori. Helicobacter 2001;6(3):249-253.
- Meher S, Duley L. Garlic for preventing pre-eclampsia and its complications. Cochrane Database Syst Rev 2006 Jul 19;3:CD006065.
- Reinhart, K. M., Talati, R., White, C. M., and Coleman, C. I. The impact of garlic on lipid parameters: a systematic review and meta-analysis. Nutr.Res.Rev. 2009;22(1):39-48.
- Ried, K., Frank, O. R., Stocks, N. P., Fakler, P., and Sullivan, T. Effect of garlic on blood pressure: a systematic review and meta-analysis. BMC.Cardiovasc.Disord. 2008;8:13.
- Sabitha P, Adhikari PM, Shenoy SM, et al. Efficacy of garlic paste in oral candidiasis. Trop Doct 2005;35(2):99-100.
- Siegel G. Long-term effect of garlic in preventing arteriosclerosis – results of two controlled clinical trials. Eur Phytojournal 2001;Symposium posters(1):1.
- Takasu J, Uykimpang R, Sunga MA, et al. Aged garlic extract is a potential therapy for sickle-cell anemia. J Nutr 2006 Mar;136(3 Suppl):803S-805S.
- Tanaka S, Haruma K, Yoshihara M, et al. Aged garlic extract has potential suppressive effect on colorectal adenomas in humans. J Nutr 2006 Mar;136(3 Suppl):821S-826S.
- You WC, Brown LM, Zhang L, et al. Randomized double-blind factorial trial of three treatments to reduce the prevalence of precancerous gastric lesions. J Natl Cancer Inst 2006 Jul 19;98(14):974-83.
- Wojcikowski K, Myers S, Brooks L. Effects of garlic oil on platelet aggregation: a double-blind placebo-controlled crossover study. Platelets 2007 Feb;18(1):29-34.
Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to . Selected references are listed below.